Since the development of the in vitro cultivation of mammalian cells the demand for large scale production of these cells has increased due to diagnostic and therapeutic potential of many of the products they produce. These useful agents include monoclonal antibodies, human growth hormone, lymphokines, erythropoietin, blood clotting factors and tissue plasminogen activators.
For many of these cellular agents mammalian cell culture provides the only viable production source. Mammalian cells have the capability to synthesize such agents with the proper configuration, correct disulfide bonding, and arrays of sugar side chains, all of which result in the desired activity of the naturally occurring agent. Therefore, many agents derived from mammalian cells are more likely to be efficacious and are less likely to be immunogenic in target mammals if expressed by bacterial or yeast fermentation.
To improve productivity, many medium formulations for feeding of mammalian cultures have been suggested (Fike et al., BioPharm. Oct.: 49-54, 1993). Some suggested medium formulations using unconcentrated nutrients significantly increase the final culture volume and thus complicate the production and recovery process (Reuveny et al. Develop. Biol. Standard 60:185-197, 1985).
Feeding with concentrated nutrients (i.e., supplements) is the preferred in vitro cultivation strategy because the product can be recovered more economically from a smaller volume of liquid, i.e., more concentrated. Methods of supplementation involve either boosting the concentration of nutrients in a basal formulation or feeding the culture with supplements. There have been only a few reports on such feeding strategies (Jo E. C. et al., UK Patent Application #2251249A, 1992; Jo E. C. et al., Biotechnol. & Bioeng. 42:1229-1237, 1993; Luan Y. T., Biotechnol. Letters 9:691:696, 1987). However, serum has to be present in the feeding media which complicates subsequent purification procedures and increases production costs.
A need exists to develop a low-cost, serum-free supplement for use in mammalian cell cultures.